Embodiments of the present application generally relate to preparatory instrumentation for implantation of an orthopedic implant or component in a bone. More particularly, but not exclusively, embodiments of the present application relate to instrumentation for implantation of a metaphyseal and/or diaphyseal implant or augment relative to, and with selectively limited freedom about, one or more reference axis(es).
Proper alignment of a replacement joint device, including components of the replacement joint device, often can contribute to attaining optimal wear resistance performance of the implanted device. Yet, anatomical variations present challenges in properly aligning the implant device for each patient. For example, during implant construct of knee replacement joints, challenges can arise with fitting a patient's intramedullary geometry with an implant, such as, for example, an intramedullary stem, while also fitting both the external geometry with a condylar replacing implant and the metaphyseal and/or diaphyseal geometry with an associated implant or augment component. Moreover, the addition of a metaphyseal and/or diaphyseal implant or augment to an implant construct often impairs the ability to adjustably fit the implant to the patient and/or attain proper alignment of the various components of the implant. Such difficulties can at times be attributed to the anatomy of the patient, the geometrical constraints of the implant, and/or constraints associated with the preparatory instrumentation. For example, geometrical constraints of the metaphyseal and/or diaphyseal implant or augment can include the inability to accommodate the placement or position of both the intramedullary stem and the condylar implant, which can attribute to difficulties in forming a junction mechanism for those, and possibly other, components of the implant.
Challenges associated with attaining proper alignment during implant construct that involves a metaphyseal and/or diaphyseal implant or augment may have, at times, been resolved by compromises in terms of the placement of at least some components of the implant device, such as, for example, the location of the condylar implant. Yet, such compromises can result in less than optimal bone coverage, which can potentially compromise loading of the construct to the cortical rim of the bone. Other compromises can include reducing the stem size in order to offset the stem position, with the area vacated by such offsetting being made up with cement. Yet, such compromises can adversely impact the life of the implant, and can be, at least in part, attributable to failures relating to subsidence, loosening, stress-shielding factors, and increased stresses on the implant device, among other failures that are associated with compromised articulation positioning.
The integrity of the implant construct can therefore be adversely impacted if the bone is not shaped, during implant surgery, to accommodate the positioning of augmenting implants at locations in which the implanted augments, such as, for example, stems, sleeves, and cones, among other augments, will not interfere with the articular component and/or other augmenting implants. Yet, the different anatomies of patients often present challenges in the ability to position augmenting implants at optimal locations. For example, in order to achieve optimal bone coverage, the articular component stem connection (post) axis can need to be at a location that is different than the stem axis. Further, the inability to attain such positioning can lead to compromises in the structure, life span, and/or performance of the implanted device, among other compromises.